Feeding structure of electrostatic chuck, method for producing the same, and method for regenerating feeding structure of electrostatic chuck

ABSTRACT

Provided is a power feeding structure of an electrostatic chuck including a lower insulation layer, an electrode layer and a surface insulation dielectric layer formed on an upper surface side of a metal substrate in order from the metal substrate, in which the lower insulation layer, the electrode layer and the surface insulation dielectric layer are not cracked easily. The power feeding structure of an electrostatic chuck includes: a through hole formed through an upper surface and a lower surface of the metal substrate; a power feeding terminal disposed in the through hole for supplying a voltage supplied from a lower surface side of the metal substrate to the electrode layer formed on the upper surface side of the metal substrate; and an insulation holding member formed of an electric insulating material for insulating an inner wall of the through hole from the power feeding terminal and for holding the power feeding terminal, and the power feeding terminal includes a power feeding end portion that protrudes to the upper surface side of the metal substrate, and a tip of the power feeding end portion is positioned at the electrode layer side with respect to an interface between the electrode layer and the lower insulation layer, and on and under an interface between the electrode layer and the surface insulation dielectric layer.

TECHNICAL FIELD

The present invention relates to a power feeding structure for feedingpower to an electrode layer of an electrostatic chuck, which is providedto a plasma treatment apparatus, an electron beam lithography, an ionimplantation apparatus or the like that is used for a manufacturingprocess of a semiconductor device, or to an ion doping apparatus or thelike that is used for manufacturing a liquid crystal panel.

BACKGROUND ART

As to the plasma treatment apparatus, the electron beam lithographyapparatus, the ion implantation apparatus or the like that is used forthe manufacturing process of a semiconductor device, or the ion dopingapparatus or the like that is used for manufacturing a liquid crystalpanel, it is required to securely hold a semiconductor wafer or a glasssubstrate that is an object to be treated without damaging thesemiconductor wafer or the glass substrate. In particular, sincecontamination of the semiconductor wafer or the glass substrate to betreated should be controlled strictly these days, most of the systemsfor clamping the semiconductor wafer or the like mechanically asconventional techniques are being replaced with the electrostatic chucksystems that utilize an electrostatic attraction force.

The electrostatic chuck includes a lower insulation layer, an electrodelayer and a surface insulation dielectric layer, which are formed on ametal substrate. The surface insulation dielectric layer constitutes anattracting surface for holding the semiconductor wafer or the glasssubstrate. Then, a high voltage potential is applied externally to theelectrode layer via power feeding terminals disposed in through holesformed through the upper and lower surfaces of the metal substrate.Thus, Coulomb force or Johnsen-Rahbeck force is generated betweencharges distributed on the surface of the surface insulation dielectriclayer (i.e., the attracting surface) and the charges polarized andinduced by the object to be treated on the attracting surface.Otherwise, a gradient force is generated by the electrostatic field, sothat the semiconductor wafer or the like as the object to be treated isattracted and held.

When etching treatment is performed on the semiconductor wafer by usinga plasma apparatus, for instance, the temperature of the semiconductorwafer will increase up to approximately 200° C. to 400° C. Therefore, inorder to cool down the wafer that is being treated to an appropriatetemperature, a refrigerant is made to flow in a conduit line providedinside the metal substrate so that the temperature increase of the waferis prevented. However, the surface insulation dielectric layer side ofthe electrostatic chuck is exposed to the high temperature while thetemperature on the metal substrate side is kept substantially to be thetemperature of the refrigerant. Therefore, a temperature gradient occursbetween them. For instance, a temperature gradient of a few hundreddegrees at highest occurs between the surface insulation dielectriclayer and the lower insulation layer. In addition, as a matter ofcourse, a temperature gradient of a few hundred degrees at highestoccurs in the electrostatic chuck itself between the time when theapparatus is operating and the time when the apparatus is stopped.

If a stress such as a heat cycle is applied to the electrostatic chuck,various problems may occur in particular with respect to a power feedingstructure for supplying a voltage to the electrode layer. Morespecifically, since an electric conductor such as the power feedingterminal or the electrode layer has a coefficient of thermal expansiondifferent from that of an insulator such as the lower insulation layerand the surface insulation dielectric layer, a crack may occur easily inthe region around the power feeding terminal where the electricconductor and the insulator contact with each other and are structurallycomplicated. This crack may be a factor causing such problem as a localdeterioration in temperature characteristics of the electrostatic chuckor particle generation or the like.

FIGS. 4( a) and 4(b) illustrate a conventional example of the powerfeeding structure of the electrostatic chuck. A through hole 7 is formedin a metal substrate 1, and a power feeding terminal 3 is disposed inthe through hole 7 via an insulation holding member 2. As illustrated inFIG. 4( b), a tip of this power feeding terminal 3 contacts with anelectrode layer 5, so that a voltage supplied to the metal substrate 1from the lower surface side is supplied to the electrode layer 3. Here,the crack as described above is likely to occur at an edge of theportion where the tip of the power feeding terminal 3 contacts with theelectrode layer 5 (crack 8 a), for instance. In addition, the crack islikely to occur also at a portion where the power feeding terminal 3,the insulation holding member 2, and a lower insulation layer 4 contactwith each other (crack 8 b).

Therefore, some methods are proposed for reducing the influence of thethermal load that is applied to the electrostatic chuck. For instance, aproposed method includes brazing a power feeding terminal for feedingpower to an electrode layer disposed in a ceramic substrate, andproviding a hollow portion on an end surface of the power feedingterminal so that a stress relieving member having a coefficient ofthermal expansion that is substantially the same as that of the ceramicsubstrate is inserted in the hollow portion (see Patent Document 1). Inaddition, another proposed method includes disposing a power feedingterminal in a through hole formed in a substrate made of a metal andceramic composite material via a casing portion made of a ceramic sothat an end surface of the power feeding terminal is flush with theupper surface of the substrate, masking the end surface of the powerfeeding terminal, forming an insulation layer by thermal sprayingtreatment, removing the masking so as to expose the end surface of thepower feeding terminal, and performing thermal spraying of a metalmaterial so as to form an electrode layer (see Patent Document 2).Further, still another proposed method includes forming a through holeformed through an inner electrode layer of a ceramic substrate from thelower side, forming a metalized layer on the inner wall of the throughhole, and brazing a power feeding terminal to be fixed in the throughhole (see Patent Document 3).

However, if the power feeding terminal is fixed by brazing as describedin Patent Documents 1 and 3, a thermal load is applied to a brazingmaterial itself so that the problem may be more complicated. Inaddition, the brazing work itself is a manual work and is not completelyreliable. On the other hand, according to the method of adjusting theend surface of the power feeding terminal disposed in the substrate tobe flush with the upper surface of the substrate, and forming theelectrode layer by the thermal spraying treatment so that the endsurface of the power feeding terminal contacts with the electrode layeras described in Patent Document 2, the work efficiency may be improved.However, it is necessary to improve the reliability more with respect tothe thermal load. In other words, since the power feeding terminalcontacts with the electrode layer by surface contact, there is still aproblem remaining in terms of reliability when a thermal load isapplied.

-   Patent Document 1: JP 11-074336 A-   Patent Document 2: JP 2003-179127 A-   Patent Document 3: JP 10-189696 A

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

The influence of the thermal load applied to the electrostatic chuck isrelated to a power feeding structure of the electrostatic chuck.Specifically, it relates to a shape of an interface between the powerfeeding terminal and the electrode layer, and to a manner in which aforce is exerted among the metal substrate, the power feeding terminal,the insulation holding member, the lower insulation layer, the electrodelayer and the surface insulation dielectric layer when the thermal loadis actually applied. A relationship between them has not been studiedsufficiently up to date.

Therefore, a task of the present invention is to provide a power feedingstructure in which a crack hardly occurs in the lower insulation layer,the electrode layer or the surface insulation dielectric layer byrelieving a thermal stress generated in the power feeding structure whenthe thermal load or a heat cycle is applied to the electrostatic chuck,so as to avoid such problem as a local deterioration in temperaturecharacteristics of the electrostatic chuck or particle generation asmuch as possible and further to increase a lifetime of the electrostaticchuck.

Means for Solving the Problem

Therefore, it is an object of the present invention to provide a powerfeeding structure of an electrostatic chuck in which a crack hardlyoccurs in a lower insulation layer, an electrode layer or a surfaceinsulation dielectric layer. In addition, it is another object of thepresent invention to provide a method of manufacturing such the powerfeeding structure of the electrostatic chuck.

Further, it is still another object of the present invention to providea method of regenerating an electrostatic chuck power feeding structurein which a used electrostatic chuck can be reused effectively byregenerating the power feeding structure of the electrostatic chuck thathas been used in various apparatuses.

Specifically, the present invention resides in a power feeding structureof an electrostatic chuck including a lower insulation layer, anelectrode layer and a surface insulation dielectric layer formed on anupper surface side of a metal substrate in order from the metalsubstrate, the power feeding structure including:

a through hole formed through an upper surface and a lower surface ofthe metal substrate;

a power feeding terminal disposed in the through hole for supplying avoltage supplied from a lower surface side of the metal substrate to theelectrode layer formed on the upper surface side of the metal substrate;and

an insulation holding member formed of an electric insulating materialfor insulating an inner wall of the through hole from the power feedingterminal and for holding the power feeding terminal,

in which the power feeding terminal includes a power feeding end portionthat protrudes to the upper surface side of the metal substrate, and atip of the power feeding end portion is positioned at an electrode layerside with respect to an interface between the electrode layer and thelower insulation layer, and on and under an interface between theelectrode layer and the surface insulation dielectric layer.

The present invention also resides in a method of manufacturing a powerfeeding structure of an electrostatic chuck including a lower insulationlayer, an electrode layer and a surface insulation dielectric layerformed on a upper surface side of a metal substrate in order from themetal substrate, the power feeding structure including:

a through hole formed through an upper surface and a lower surface ofthe metal substrate;

a power feeding terminal disposed in the through hole for supplying avoltage supplied from a lower surface side of the metal substrate to theelectrode layer formed on the upper surface side of the metal substrate;and

an insulation holding member formed of an electric insulating materialfor insulating an inner wall of the through hole from the power feedingterminal and for holding the power feeding terminal,

the method including the steps of:

forming the lower insulation layer by thermal spraying of ceramic powderonto the upper surface side of the metal substrate having the throughhole in which the power feeding terminal is disposed via the insulationholding member, a part of the power feeding terminal protruding to theupper surface side of the metal substrate;

forming the electrode layer by thermal spraying of metal powder so thata tip of a power feeding end portion of the power feeding terminalprotruding to the upper surface side of the metal substrate is embeddedor the electrode layer is flush with the tip of the power feeding endportion; and

forming the surface insulation dielectric layer by thermal spraying ofceramic powder.

Further, the present invention resides in a method of regenerating apower feeding structure of an electrostatic chuck including a lowerinsulation layer, an electrode layer and a surface insulation dielectriclayer formed on a upper surface side of a metal substrate in order fromthe metal substrate, the power feeding structure including:

a through hole formed through an upper surface and a lower surface ofthe metal substrate;

a power feeding terminal disposed in the through hole for supplying avoltage supplied from a lower surface side of the metal substrate to theelectrode layer formed on the upper surface side of the metal substrate;and

an insulation holding member formed of an electric insulating materialfor insulating an inner wall of the through hole from the power feedingterminal and for holding the power feeding terminal,

the method including the steps of:

removing the surface insulation dielectric layer, the electrode layerand the lower insulation layer from the metal substrate of a usedelectrostatic chuck;

forming the lower insulation layer by thermal spraying of ceramic powderonto the upper surface side of the metal substrate having the throughhole in which the power feeding terminal is disposed via the insulationholding member, a part of the power feeding terminal protruding to theupper surface side of the metal substrate;

forming the electrode layer by thermal spraying of metal powder so thata tip of a power feeding end portion of the power feeding terminalprotruding to the upper surface side of the metal substrate is embeddedor the electrode layer is flush with the tip of the power feeding endportion; and

forming the surface insulation dielectric layer by thermal spraying ofceramic powder.

Note that an object to be treated such as a semiconductor wafer or aglass substrate is placed and attracted on the side of the surfaceinsulation dielectric layer of the electrostatic chuck in the presentinvention, and that the side of the surface insulation dielectric layeron which the object to be treated is placed is referred to as a uppersurface side while the opposite side is referred to as a lower surfaceside when the upper or lower side of the metal substrate is referred to.

Effects of the Invention

In the power feeding structure of the electrostatic chuck according tothe present invention, the tip of the power feeding end portion of thepower feeding terminal is positioned at the electrode layer side withrespect to the interface between the electrode layer and the lowerinsulation layer, and on and under the interface between the electrodelayer and the surface insulation dielectric layer. Therefore, the powerfeeding terminal contacts with the electrode layer securely so that theoccurrence of a crack can be prevented. In particular, the power feedingend portion of the power feeding terminal is formed like a protrusionincluding a top surface having a predetermined area at the tip anddecreasing its diameter gradually toward the tip. Thus, the stress thatis applied to the lower insulation layer can be dispersed, and a crackin the surface insulation dielectric layer, the electrode layer and thelower insulation layer due to a thermal load caused by a heat gradientof the power feeding structure and a thermal load caused by the heatcycle can be suppressed, so that a durable electrostatic chuck can beprovided, which can avoid such problem as the local deterioration of thetemperature characteristics of the electrostatic chuck or the particlegeneration as much as possible. In addition, it is possible to increasethe lifetime of the electrostatic chuck.

In addition, according to the regeneration method of the electrostaticchuck power feeding structure of the present invention, a usedelectrostatic chuck can be reused effectively by applying the powerfeeding structure of the present invention to the electrostatic chuckthat has been used in various apparatuses. It is also possible toincrease its lifetime.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional explanatory diagram illustrating a powerfeeding structure of an electrostatic chuck according to the presentinvention.

FIG. 2 are cross sectional explanatory diagrams illustrating positionalrelationships of the tip of the power feeding end portion 3 a withrespect to the electrode layer.

FIG. 3 is a cross sectional explanatory diagram of the power feedingstructure in which a part of the insulation holding member (on the sideof the lower insulation layer 4) is formed of a porous ceramic.

FIG. 4( a) is a cross sectional explanatory diagram of a conventionalelectrostatic chuck, and FIG. 4( b) is a (partial) enlarged view of apower feeding structure.

DESCRIPTION OF SYMBOLS

-   -   1: metal substrate, 2: insulation holding member, 3: power        feeding terminal, 3 a: power feeding end portion, 3 b: top        surface, 3 c: side surface, 4: lower insulation layer, 5:        electrode layer, 6: surface insulation dielectric layer, 7:        through hole, 8 a, 8 b: crack, l₁: interface between electrode        layer and lower insulation layer, l₂: interface between        electrode layer and surface insulation dielectric layer, x:        position of tip of power feeding end portion

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a preferred embodiment of the present invention isdescribed in detail with reference to the attached drawings.

First, a power feeding structure of an electrostatic chuck of thepresent invention is described. FIG. 1 is a cross sectional explanatorydiagram illustrating a power feeding structure of the electrostaticchuck, and it is an enlarged view of the power feeding structure of theelectrostatic chuck including a lower insulation layer 4, an electrodelayer 5 and a surface insulation dielectric layer 6 formed on a uppersurface of a metal substrate 1 in order from the metal substrate 1. Morespecifically, this power feeding structure includes a through hole 7formed through the upper surface and a lower surface of the metalsubstrate 1, a power feeding terminal 3 disposed in the through hole 7so as to supply a voltage supplied from the lower surface side of themetal substrate 1 to the electrode layer 5 formed on the upper surfaceside, and an insulation holding member 2 formed of an electricinsulating material for insulating the inner wall of the through hole 7from the power feeding terminal 3 and holding the power feeding terminal2.

Further, the power feeding terminal 3 has a power feeding end portion 3a protruding toward the upper surface side of the metal substrate 1. Atip of this power feeding end portion 3 a is positioned on the electrodelayer 5 side with respect to the interface between the electrode layer 5and the lower insulation layer 4, and on and under the interface betweenthe electrode layer 5 and the surface insulation dielectric layer 6. Inother words, when the interface between the electrode layer 5 and thelower insulation layer 4 is denoted by l₁ while the interface betweenthe electrode layer 5 and the surface insulation dielectric layer 6 isdenoted by l₂, the position x of the tip of the power feeding endportion 3 a satisfies the relational expression “l₁<x≦l₂” in the presentinvention.

This relationship is described in detail with reference to FIG. 2. InFIG. 2( a), the position x of the tip of the power feeding end portion 3a is on the interface between the electrode layer 5 and the lowerinsulation layer 4 (x=l₁), and x does not satisfy the above relationalexpression. On the other hand, in FIG. 2( d), the position x is abovethe interface between the electrode layer 5 and the surface insulationdielectric layer 6 (x>l₂), and x does not satisfy the above relationalexpression. If the tip of the power feeding end portion 3 a reaches theinside of the surface insulation dielectric layer 6, the surfaceinsulation dielectric layer becomes thin at the position, so that thereis a possibility that the insulating properties against high voltagecannot be maintained. On the contrary, in FIG. 2( b), the tip of thepower feeding end portion 3 a is positioned inside the electrode layer 5(x>l₁), and x satisfies the above relational expression. Further, inFIG. 2C, the position x is on the interface between the electrode layer5 and the surface insulation dielectric layer 6 (x=l₂), and x satisfiesthe above relational expression.

Further, in the present invention, as long as the position x of the tipof the power feeding end portion 3 a satisfies the above relationalexpression, a shape of the tip of the power feeding end portion 3 a isnot limited to a particular shape. It may have a top surface of apredetermined area or may have a vertex. It is preferable that the powerfeeding end portion 3 a of the power feeding terminal 3 should include atop surface 3 b having a predetermined area at the tip thereof and havea protruding shape whose diameter decreases gradually toward the tip.Since the power feeding end portion 3 a has the protruding shape and thetop surface 3 b at the tip thereof, the power feeding terminal 3contacts securely with the electrode layer 5 so that a possibility ofoccurrence of a discharge or the like can be eliminated as much aspossible. Further, since the power feeding end portion 3 a has adiameter decreasing gradually toward the tip, a side surface 3 c of thepower feeding end portion contacts with the lower insulation layer 4 bya fit-in relationship, so that a stress caused by a thermal load can bedispersed in a relatively wide range for preventing occurrence of acrack. Note that a concrete size of the power feeding terminal 3 dependson a size of the semiconductor wafer or the like to be treated or ashape of the apparatus equipped with the electrostatic chuck, or thelike, though an outer diameter thereof is usually (φ2 to φ10 mm. Inaddition, if the top surface is formed at the tip of the power feedingend portion 3 a, it is preferable to have a circular shape having adiameter of 2 to 4.5 mm, for example.

In addition, it is preferable for the side surface 3 c of the powerfeeding end portion that at least the portion contacting with the lowerinsulation layer 4 is a curved surface having a predetermined curvature.Thus, the above-mentioned effect of dispersing the stress can beenhanced more. Here, a radius of curvature of the curved surface is notlimited to a particular value. Although it depends on a length of thepower feeding end portion 3 a or a size of the top surface formed at thetip thereof, it should be determined from a viewpoint of dispersing thestress or an overall consideration of a contact area with the electrodelayer. Specifically, a range of approximately R0.25 to R1.5 mm ispreferable, so that a risk of a discharge can be eliminated as much aspossible. Note that the shape of the power feeding end portion 3 ahaving a diameter decreasing toward the tip in the present inventionmeans to exclude the case where the power feeding end portion 3 a has adiameter increasing toward the tip. In other words, it is allowed tohave a part having the same diameter. For instance, as to the powerfeeding end portion 3 a disposed inside the electrode layer 5, itsdiameter may be the same to the tip.

Next, a manufacturing method for the power feeding structure describedabove is exemplified while the present invention is further described.First, the metal substrate 1 including the power feeding terminal 3disposed in the through hole 7 via the insulation holding member 2 isprepared. On this occasion, a part of the power feeding terminal 3 ismade to protrude from the upper surface side of the metal substrate 1,so that the power feeding end portion 3 a is formed. Then, ceramicpowder such as alumina or aluminum nitride is sprayed thermally onto theupper surface side of the metal substrate 1 so as to form the lowerinsulation layer. Here, a purity of the ceramic powder is preferablywithin a range of 99.9% to 99.99%. In addition, a film thickness of thelower insulation layer 4 depends on an environment in which theapparatus is used, though it is preferably within a range of 200 to 500μm in general.

The material of the power feeding terminal 3 is not limited to aparticular material, though it is preferable to be metal titanium from aviewpoint of a corrosion resistance. Further, it is sufficient that themetal substrate is a normally used one made of aluminum, copper,stainless steel, various alloys including them, or a metal matrixcomposite (MMC) of ceramic and metal, for example. In addition, thepower feeding terminal 3 and the insulation holding member 2, as well asthe insulation holding member 2 and the inner wall of the through hole 7may be glued to each other, respectively, by using epoxy adhesive orsilicon adhesive, for example.

On the other hand, the material of the insulation holding member 2 maybe resin, machinable ceramic, alumina ceramic, alumina ceramic formed bythe thermal spray, or the like, for example. It is preferable that atleast the part thereof exposed to the upper surface side of the metalsubstrate should be made of porous ceramic. FIG. 3 illustrates a crosssectional explanatory diagram in the case where a part of the insulationholding member 2 on the side of the lower insulation layer 4 is formedof a porous ceramic 2 a. In this way, if the part exposed to the uppersurface side of the metal substrate 1 is formed of the porous ceramic,and if the lower insulation layer 4 is formed by the thermal spray ofthe ceramic powder, the ceramic powder is sprayed thermally into theholes of the porous material so as to form a firm joint portion. Notethat the effect obtained when the part on the side of the lowerinsulation layer 4 is made of the porous ceramic so as to contact withthe lower insulation layer can be obtained independently of a positionof the tip of the power feeding end portion or the shape of the powerfeeding terminal. However, if it is combined with the position or theshape of the tip of power feeding end portion according to the powerfeeding structure of the present invention, the effect of suppressingoccurrence of a crack can be enhanced more.

If the power feeding terminal is made of metal titanium, for instance, acoefficient of thermal expansion of titanium is 8.6×10⁻⁶/° C., which isusually larger than that of a material forming the lower insulationlayer or the electrode layer described later (for example, 6.5×10⁻⁶/° C.of alumina, and 4.5×10⁻⁶/° C. of tungsten). Therefore, when a thermalload is applied to the power feeding terminal 3, a stress is generatedin the direction of the insulation holding member 2. Then, a force ofseparating the lower insulation layer 4 and the insulation holdingmember 2 from each other is generated, which may cause a crack.Therefore, as described above, the insulation holding member 2 and thelower insulation layer 4 are made of equivalent materials, and the jointat the interface between them is made firmer, so that occurrence of acrack can be prevented effectively. In addition, a porosity of theporous ceramic is preferably within a range of 0.5% to 30%. Inparticular, a porosity within a range of 5% to 10% is more preferablefor securing continuity with the lower insulation layer 4 easily andfrom a viewpoint of sealing processability of pores using silicon, epoxyresin, acrylic resin or the like. Further, when the material of theinsulation holding member 2 is the porous ceramic, at least only thepart contacting with the lower insulation layer 4 may be formed of theporous ceramic as illustrated in FIG. 3. Alternatively, the entireinsulation holding member 2 may be formed of the porous ceramic.

Next, metal powder is sprayed thermally onto the lower insulation layer4 formed as described above so that the electrode layer 5 is formed. Onthis occasion, the electrode layer 5 is formed so that the position x ofthe tip of the power feeding end portion 3 a of the power feedingterminal 3 protruding to the upper surface side of the metal substrate 1satisfies the relational expression of “l₁<x≦l₂”, i.e., so that the tipof the power feeding end portion 3 a is embedded in the electrode layer5, or so that the tip of the power feeding end portion 3 a forms thesame plane as the electrode layer 5. There is no particular limitationfor the metal powder that is used for forming the electrode layer 5.However, it is preferable to be a refractory metal from a viewpoint ofdurability or easiness of the thermal spray. Specifically, molybdenum ortungsten is preferably used. A purity of the metal powder to be used ispreferably 99.99% or higher. In addition, a film thickness of theelectrode layer 5 depends on the environment in which the apparatus isused, but is preferably 20 to 60 μm in general. Note that it is possibleto form the electrode layer 5 by applying paste of the refractory metaldescribed above, but this method is inferior to the thermal spray in theviewpoint of durability.

Then, the ceramic powder such as alumina, aluminum nitride or the likeis sprayed thermally onto the electrode layer 5 so that the surfaceinsulation dielectric layer 6 is formed. Thus, the electrostatic chuckhaving the power feeding structure of the present invention can beobtained. A purity of the ceramic powder forming the surface insulationdielectric layer 6 is similar to the case of the lower insulation layer4. In addition, a film thickness of the surface insulation dielectriclayer 6 depends on the environment in which the apparatus is used, butis preferably 200 to 500 μm in general. Further, the surface of thesurface insulation dielectric layer 6 for attracting a semiconductorwafer or the like is preferably processed by flattening treatment sothat the flatness thereof is within a range of 5 to 10 μm. In addition,the exposed surfaces of the lower insulation layer 4, the electrodelayer 5 and the surface insulation dielectric layer 6 may be processedby vacuum impregnation treatment using silicon resin, epoxy resin, oracrylic resin, for example, for a purpose of sealing pores formed by thethermal spray.

In addition, it is possible to utilize the manufacturing method of thepower feeding structure of the present invention for regenerating thepower feeding structure of a used electrostatic chuck. Morespecifically, the surface insulation dielectric layer 6, the electrodelayer 5 and the lower insulation layer 4 are removed mechanically orchemically from the metal substrate 1 of the used electrostatic chuck,so as to prepare a metal substrate including the power feeding terminaldisposed in the through hole and a part of the power feeding terminalprotruding to the upper surface side of the metal substrate. Then, thelower insulation layer 4, the electrode layer 5 and the surfaceinsulation dielectric layer 6 are formed similarly to the manufacturingmethod of the power feeding structure, so that the electrostatic chuckhaving the power feeding structure of the present invention can beregenerated.

Prior to the step of forming the electrode layer, a height of the powerfeeding end portion of the power feeding terminal may be adjusted, or itmay be shaped to be like a protrusion including a top surface having apredetermined area at the tip thereof and a diameter decreasinggradually toward the tip. In addition, when the surface insulationdielectric layer 6, the electrode layer 5 and the lower insulation layer4 are removed from the used electrostatic chuck, the insulation holdingmember 2 may also be removed so as to exchange it with a new one. Inthis case, at least the part exposed to the upper surface side of themetal substrate 1 may be made of porous ceramic. Note that the usedelectrostatic chuck includes one that has been used in a certainapparatus for a predetermined period of time and finished its lifetimeas a product, and one in which the surface insulation dielectric layer 6is deteriorated or a crack has occurred due to a certain trouble, orthat cannot be used any more due to another damage or wearing out beforereaching the lifetime.

Example 1

An example of the electrostatic chuck having the power feeding structureillustrated in FIG. 1 is described. A metal substrate 1 made of aluminumhaving a diameter of φ230 mm and a thickness of 48 mm was prepared. Aupper surface side of this metal substrate 1 has a flatness of 10 μm orsmaller. The through hole 7 having a maximum diameter of φ11.1 mm isformed in the metal substrate 1 so as to pierce the upper surface andthe lower surface thereof. In addition, a plurality of conduits (notshown) are formed. Some of the conduits are used for cooled water topass through so as to cool the metal substrate 1 directly while othersare used for leading gas such as helium to the underside of the objectto be treated such as a semiconductor wafer or the like disposed on theelectrostatic chuck.

The power feeding terminal 3 is obtained by machining a titaniummaterial, which has a maximum outer diameter of φ5 mm and a length of 47mm. In addition, the top surface 3 b having a diameter of 3 mm is formedat the tip of the power feeding end portion 3 a, and the side surface 3c of the power feeding end portion 3 a is a curved surface having aradius of curvature R of 1 mm. This power feeding terminal 3 is disposedin the through hole 7 via the insulation holding member 2 made of resinso that the power feeding end portion 3 a is formed protruding to theupper surface side of the metal substrate 1 by 350 μm. The power feedingterminal 3 and the insulation holding member 2, as well as theinsulation holding member 2 and the inner wall of the through hole 7 arerespectively glued to each other by an epoxy adhesive (not shown). Notethat an outer diameter of the insulation holding member 2 illustrated inFIG. 1 is 11 mm.

As described above, the power feeding terminal 3 was disposed in thethrough hole 7, and alumina of a purity of 99.99% was sprayed thermallyonto the upper surface side of the metal substrate 1 from which thepower feeding end portion 3 a of the power feeding terminal 3 wasprotruded so that the lower insulation layer 4 having a thickness of 300μm was formed. Next, tungsten of a purity of 99.99% was sprayedthermally for forming the electrode layer 5 having a thickness of 50 μmso as to be the same height as the top surface 3 b of the power feedingterminal 3. Note that unnecessary alumina was removed before the step offorming the electrode layer because alumina that had been used forforming the lower insulation layer 4 was deposited on the power feedingterminal 3.

Next, alumina of a purity of 99.99% was sprayed thermally onto theelectrode layer 5 so as to form a surface insulation dielectric layer 6having a thickness of 300 μm. After that, the surface insulationdielectric layer 6 was treated so that its surface flatness would fallwithin a range of 5 to 10 μm. In addition, the vacuum impregnationtreatment was performed using silicon for sealing the exposed surfacesof the lower insulation layer 4, the electrode layer 5 and the surfaceinsulation dielectric layer 6 so that the electrostatic chuck wascompleted. Note that atmospheric thermal spray was performed as thethermal spray onto the lower insulation layer 4, the electrode layer 5and the surface insulation dielectric layer 6.

Example 2

Next, an example of the case where the power feeding structure of theused electrostatic chuck is regenerated is described. First, the surfaceinsulation dielectric layer 6, the electrode layer 5, and the lowerinsulation layer 4 were removed from the used electrostatic chuck bymechanical cutting that included a manual work partially. When the lowerinsulation layer 4 was removed from the metal substrate 1, the uppersurface side of the metal substrate 1 was removed by a thickness withina range of 0.1 to 0.5 mm to obtain the flatness of 10 μm or smaller.

Next, as illustrated in FIG. 1, the power feeding end portion of thepower feeding terminal was processed by using a ball end mill, so thatthe top surface 3 b having a diameter of 3 mm was formed at the tipthereof. In addition, the side surface 3 c having a radius of curvatureof R1 mm was formed. Then, the lower insulation layer 4, the electrodelayer 5 and the surface insulation dielectric layer 6 were formedsimilarly to Example 1 except that a film thickness of the lowerinsulation layer 4 was made to be 300 μm+α (α corresponds to thethickness by which the upper surface side of the metal substrate 1 wasremoved), so that the electrostatic chuck having the power feedingstructure of the present invention was regenerated. Note that theabove-mentioned α is a thickness adjustment amount of the metalsubstrate between before and after the regeneration. For instance, ifthe metal substrate is ground to remove a thickness of 0.5 mm, the lowerinsulation layer 4 is formed as α=0.5 mm. As a result, the capacity ofthe electrostatic chuck can be made equal between before and after theregeneration.

Example 3

An example of the electrostatic chuck having the power feeding structureillustrated in FIG. 3 is described. The metal substrate 1 and the powerfeeding terminal 3 that are similar to those of Example 1 were prepared,and the power feeding terminal 3 was disposed in the through hole 7 ofthe metal substrate 1 via the insulation holding member 2. On thisoccasion, the insulation holding member 2 a made of alumina having aporosity of 5-10% was used for the lower insulation layer 4 side. Thisinsulation holding member 2 a made of alumina is made of the samematerial as that of the lower insulation layer 4 to be formed later, andhas an outer diameter of 11 mm and a length of 10 mm. Other conditionswere the same as Example 1.

Next, alumina powder having a purity of 99.99% was sprayed thermallyonto the upper surface side of the metal substrate 1 from which theinsulation holding member 2 a made of alumina is exposed, so that thelower insulation layer 4 having a film thickness of 300 μm was formed.On this occasion, apart of the lower insulation layer 4 contacted withthe insulation holding member 2 a made of alumina so as to form a firmjoint surface. After that, similarly to Example 1, the electrostaticchuck having the power feeding structure of the present invention wascompleted.

Example 4

An example of regenerating the electrostatic chuck having the powerfeeding structure illustrated in FIG. 3 by using the electrostatic chuckof the conventional example illustrated in FIG. 4 is described.

First, similarly to Example 2, the surface insulation dielectric layer6, the electrode layer 5, and the lower insulation layer 4 were removedfrom the used electrostatic chuck. After that, the used power feedingterminal and the used insulation holding member were removed from thethrough hole 7 of the metal substrate 1. Next, the upper surface side ofthe metal substrate 1 was ground to remove a thickness within a range of0.1 to 0.5 mm to obtain the flatness of 10 μm or smaller. In addition,similarly to Example 2, the power feeding end portion of the powerfeeding terminal was processed by the ball end mill so as to form thetop surface 3 b having a diameter of 3 mm at the tip. In addition, thecurved surface 3 c having a radius of curvature of R1 mm was formed onthe side surface.

Then, the power feeding terminal was disposed in the through hole 7 ofthe metal substrate 1 via the insulation holding member 2. On thisoccasion, the insulation holding member 2 a made of alumina having aporosity of 5% to 10% was used for the lower insulation layer 4 side.This insulation holding member 2 a made of alumina is made of the samematerial as that of the lower insulation layer 4 to be formed later, andhas an outer diameter of 11 mm and a length of 10 mm. Other conditionswere the same as Example 1.

Next, alumina powder having a purity of 99.99% was sprayed thermallyonto the upper surface side of the metal substrate 1 from which theinsulation holding member 2 a made of alumina was exposed, so that thelower insulation layer 4 was formed with a film thickness of 300 μm+α (αcorresponds to a thickness by which the upper surface side of the metalsubstrate 1 was removed). On this occasion, a part of the lowerinsulation layer 4 contacted with the insulation holding member 2 a madeof alumina so as to form a firm joint surface. Subsequent processes wereperformed similarly to Example 1 to regenerate the electrostatic chuckhaving the power feeding structure of the present invention.

INDUSTRIAL APPLICABILITY

According to the present invention, it is possible to provide the powerfeeding structure in which a crack hardly occurs in the lower insulationlayer, the electrode layer or the surface insulation dielectric layer byrelieving a thermal stress generated in the power feeding structure whena thermal load or a heat cycle is applied to the electrostatic chuck.Therefore, it is possible to avoid such problem as a local deteriorationin temperature characteristics of the electrostatic chuck or particlegeneration as much as possible and further to increase a lifetime of theelectrostatic chuck. Therefore, not only manufacturing of a newelectrostatic chuck but also regeneration of an electrostatic chuckhaving the power feeding structure of the present invention is possibleby utilizing a used electrostatic chuck. Thus, the used electrostaticchuck, which has been discarded in some cases conventionally, can bereused effectively. In addition, without limiting to the power feedingstructure of the electrostatic chuck in particular, the presentinvention can be applied also to the power feeding structure of otherdevice such as an engine of an automobile, a high heat furnace, or anelectric power turbine, to which a similar thermal load or a similarmechanical load may be applied.

1. A power feeding structure of an electrostatic chuck including a lowerinsulation layer, an electrode layer and a surface insulation dielectriclayer formed on an upper surface side of a metal substrate in order fromthe metal substrate, the power feeding structure comprising: a throughhole formed through an upper surface and a lower surface of the metalsubstrate; a power feeding terminal disposed in the through hole forsupplying a voltage supplied from a lower surface side of the metalsubstrate to the electrode layer formed on the upper surface side of themetal substrate; and an insulation holding member formed of an electricinsulating material for insulating an inner wall of the through holefrom the power feeding terminal and for holding the power feedingterminal, wherein the power feeding terminal includes a power feedingend portion that protrudes to the upper surface side of the metalsubstrate, and a tip of the power feeding end portion is positioned atan electrode layer side with respect to an interface between theelectrode layer and the lower insulation layer, and on and under aninterface between the electrode layer and the surface insulationdielectric layer.
 2. A power feeding structure of an electrostatic chuckaccording to claim 1, wherein the power feeding end portion of the powerfeeding terminal includes a top surface having a predetermined area atthe tip and has a protruding shape whose diameter decreases graduallytoward the tip.
 3. A power feeding structure of an electrostatic chuckaccording to claim 2, wherein a side surface of the power feeding endportion of the power feeding terminal that contacts with at least thelower insulation layer is a curved surface having a predeterminedcurvature.
 4. A power feeding structure of an electrostatic chuckaccording to claim 1, wherein the power feeding terminal is made ofmetal titanium.
 5. A power feeding structure of an electrostatic chuckaccording to claim 1, wherein at least a part of the insulation holdingmember exposed to the upper surface side of the metal substrate is madeof porous ceramic, and ceramic powder is sprayed thermally so that thelower insulation layer contacts with the porous ceramic.
 6. A method ofmanufacturing a power feeding structure of an electrostatic chuckincluding a lower insulation layer, an electrode layer and a surfaceinsulation dielectric layer formed on a upper surface side of a metalsubstrate in order from the metal substrate, the power feeding structureincluding: a through hole formed through an upper surface and a lowersurface of the metal substrate; a power feeding terminal disposed in thethrough hole for supplying a voltage supplied from a lower surface sideof the metal substrate to the electrode layer formed on the uppersurface side of the metal substrate; and an insulation holding memberformed of an electric insulating material for insulating an inner wallof the through hole from the power feeding terminal and for holding thepower feeding terminal, the method comprising the steps of: forming thelower insulation layer by thermal spraying of ceramic powder onto theupper surface side of the metal substrate having the through hole inwhich the power feeding terminal is disposed via the insulation holdingmember, a part of the power feeding terminal protruding to the uppersurface side of the metal substrate; forming the electrode layer bythermal spraying of metal powder so that a tip of a power feeding endportion of the power feeding terminal protruding to the upper surfaceside of the metal substrate is embedded or the electrode layer is flushwith the tip of the power feeding end portion; and forming the surfaceinsulation dielectric layer by thermal spraying of ceramic powder.
 7. Amethod of manufacturing a power feeding structure of an electrostaticchuck according to claim 6, wherein at least a part of the insulationholding member exposed to the upper surface side of the metal substrateis made of porous ceramic, and the lower insulation layer is formed soas to contact with the porous ceramic.
 8. A method of regenerating apower feeding structure of an electrostatic chuck including a lowerinsulation layer, an electrode layer and a surface insulation dielectriclayer formed on a upper surface side of a metal substrate in order fromthe metal substrate, the power feeding structure including: a throughhole formed through an upper surface and a lower surface of the metalsubstrate; a power feeding terminal disposed in the through hole forsupplying a voltage supplied from a lower surface side of the metalsubstrate to the electrode layer formed on the upper surface side of themetal substrate; and an insulation holding member formed of an electricinsulating material for insulating an inner wall of the through holefrom the power feeding terminal and for holding the power feedingterminal, the method comprising the steps of: removing the surfaceinsulation dielectric layer, the electrode layer and the lowerinsulation layer from the metal substrate of a used electrostatic chuck;forming the lower insulation layer by thermal spraying of ceramic powderonto the upper surface side of the metal substrate having the throughhole in which the power feeding terminal is disposed via the insulationholding member, a part of the power feeding terminal protruding to theupper surface side of the metal substrate; forming the electrode layerby thermal spraying of metal powder so that a tip of a power feeding endportion of the power feeding terminal protruding to the upper surfaceside of the metal substrate is embedded or the electrode layer is flushwith the tip of the power feeding end portion; and forming the surfaceinsulation dielectric layer by thermal spraying of ceramic powder.
 9. Amethod of regenerating a power feeding structure of an electrostaticchuck according to claim 8, further comprising the step of processingthe power feeding end portion of the power feeding terminal so as toinclude a top surface having a predetermined area on the tip and to havea protruding shape whose diameter decreases toward the tip, prior to thestep of forming the electrode layer.